A promotion campaign is being planned to encourage people to reduce heat in their houses at night. In order to measure the campaign's impact, we want to determine the proportion of people who reduce their heat at night, π. A telephone sample will be taken before and after the campaign.
a. What sample size is required if an accuracy of ±0.03 is desired at a 90 percent confidence level?
b. At a 95 percent confidence level?
c. How would your answer to part (b) change if you knew that the proportion would not exceed 0.3? What if it would not exceed 0.1?
d. Assume that a "before" measure was taken with a sample size of 400 and the sample proportion was 0.3. Generate a 90 percent confidence-level estimate for the population proportion.